This invention relates to an electromagnetically actuated clutch which is selectively operable to couple and uncouple a rotary shaft and a rotary output member. More specifically, the invention relates to a clutch of the type in which a rotatable armature is coaxial with the shaft and is drawn axially toward the shell of an electromagnetic field by magnetic flux when the field is excited. To draw the armature toward the field, the flux cuts across a narrow air gap between the field shell and the armature.
When the armature is drawn toward the field shell, the armature pulls on an axially movable pressure plate and causes the plate to press the discs of a disc pack into frictional engagement with one another and with an axially fixed pressure plate. Such frictional engagement causes the output member to rotate in unison with the input shaft.